Process of preparing color-stable fatty acids



Patented Dec. 1, 1936 UNITED STATES 2,062,837 JROOESS OF PREPARINGCOLOR-STABLE FATTY ACIDS Madison L. Sheely, Des Plaines, Ill., assignorto Armour and Company, tion of Illinois Chicago, 111., a corpora- NoDrawing. Application October 16, 1935, Serial No. 45,360

13 Claims.

This invention relates to processes of preparing color-stable fattyacids, and it comprises processes wherein crude fatty acid-containingmaterials, such as garbage grease, acidulated fatty acid foots,

crude fatty acids from the splitting of fats, and similar materialscontaining substantial amounts of free fatty acids, are treated, priorto distillation, to render color-forming bodies in such materials', lesseffective to discolor the distilled fatty acids, to improve the odor andto stabilize the acids against rancidity, and the thus treated crudeniateriais then distilled.

Free fatty acids, such as oleic, palmitic, stearic, lauric, linoleic,linolenic, and others are substances produced in enormous quantitiesfrom fatty acid-containing materials. Hitherto the better grades offatty acids, namely those having but little color, or substantiallycolorless, have been commercially produced only from rather high qualityraw materials. The problem of color is a serious one in the industry.

Many crude products containing commercial quantitiesof free and combinedfatty acids would be extremely valuable sources of high grade fattyacids were it not for the fact that such fatty acids, when distilledwith steam under vacuum in the usual way, rapidly discolor.

Black cottonseed fatty acids, acidulated fatty acid foots, garbagegrease, brown grease, and sim- 30 ilar crude materials, all containcommercially important quantities of free fatty acids, and these fattyacids can be distilled therefrom in the usual way. These sources offree, distillable fatty acids, however, contain color-forming bodieswhich ap- 35 pear to distil over with the fatty acids. Although a fattyacid distilled from such a crude, highly colored mixture, may initiallybe quite colorless,

or substantially so, in the course of aging in storage, or in transit,the fatty acid soon colors.

40 This phenomenon has greatly limited the uses to which distilled fattyacids from these crude sources can be put, and any process of preventingsuch coloration, in other words, of rendering the distilled fatty acidscolor-stable, would be of great economic significance in the art.Various attempts to bleach the distilled, colored fatty acids have beensuggested. Decolorizing agents, bleaching solutions, etc., have beenused with indifferent success, and the problem has hitherto beenregarded as most difficult of solution. Although the art has continuedto distil' free fatty acids from these very crude, in many instances,almost waste, sources, the fatty acids obtained have naturally been oflow grade. 55 One source of distillable free fatty acids, yieldinghowever, only low grade products, is that material collectively referredto as acidulated fatty acid foots. 'Most naturally occurring vegetableand animal oils are predominantly glycerides as sociated with some freefatty acid, color bodies,

albuminous material and other impurities. In the refining of such fatsand oils to fit them for use in edible products for instance, they arecustomarily treated with alkaline solutions. The alkali reacts with thefree fatty acids to form soap and dissolves coloring matter from theoil. The "foots thus formed settle to the bottomof the tank carryingwith them some entrained neutral oil. There may also be somesaponification of the fat, although this is ordinarily restricted. Thealkali washings are removed from the treated fat or oil and neutralizedwith a mineral acid. The acidulated products, after washing with waterand drying, are the acidulated foots. Cottonseed, corn oil, coconut oil,and many others are alkalirefined in this way and great quantities ofacidulated foots accumulate. All of the foots are highly colored.Acidulated cottonseed foots may contain from 50 to 90 percent of freefatty acids calculated as oleic, and from 1 to 50 percent of neutral fat(glycerides) extracted along with the fattyv acids from thealkali-treated oil. An aver- -age analysis is about 70 percent freefatty acid, and about percent neutral fat, the rest being moisture (1percent), coloring matter and other impurities.

Acidulated coconut foots will average about 50 percent free fatty acid,as lauric, about 47 percent neutral fat, and about 1 percent moisture,the rest being coloring matter and other impurities.

Ordinarily the free fatty acid in such materials is first distilledtherefrom in ways well known, and then the still residue is hydrolyzed,or split to liberate further quantities of free acids from the neutralfat. But, as stated, fatty acids distilled from such sources, are ofpoor grade.

Anothercommercial source of fatty acids is waste grease-like materialssuch as garbage grease and brown grease. These products are of lowgrade, as would be expected, and their content of free fatty acid willaverage, in the case of brown grease, about 25 percent expressed asoleic, and in the case of garbage grease, about 37 percent, as oleic,the remainder being mostly neutral fat, about 1 percent of moisture, anda few percent of coloring matter and other impurities.

The problem of color stability in distilled fatty acids is notrestricted tothe very low grade fatty acid-containing materials justdescribed. Disadvantageous discoloration may occur in the distillationof fatty acids obtained from the hydrolysis or saponification of neutralfats, and may even occur in the distillation of oleic acid, or red oil,obtained from high grade fats such as tallow. It is also a problem ofsignificance in connection with. the distillation of fatty acids madesynthetically, as by treatment of petroleum products.

Just why fatty acids distilled from crude sources should develop coloris not at all clear.

There have been theories advanced, and attempts have been made todetermine the nature of the coloring matter. But what it actually is isstill unsettled. The fact remains, however, that color does develop. Thecolor bodies may be highly complex organic compounds distillable alongwith the fatty acids. Possibly they are latent color bodies. That is tosay, they may initially be colorless, but exposure to air and light, orother atmospheric influences initiates molecular changes therein wherebycolored compounds are formed. Or they may be both initially colored andlatent color bodies, so that they initially color the distilled fattyacids, and the color is increased as the latent color bodies undergochange to the colored form. Conceivably they are highly reactive,unsaturated compounds.

To illustrate the peculiar behavior of distilled fatty acids, I distilthe acids from an ordinary commercial sample of so-called autoclavedblack cottonseed fatty acids. This is a material with which the art isfamiliar, and is a commercial product. The initially distilled acidsshow, in a Lovibond colorimeter, a red of 0.9 and a yellow of 8 whenread through a 1%" column. (All color readings hereafter given are readthrough a 1% column). After this initially distilled acid is submittedto an accelerated aging test by heating for one hour at 120 C. the colorof the distillate is red 11 and yellow 30. The accelerated aging testindicates quickly the expected color stability of the fatty acids.Similar rapid coloration on accelerated aging is characteristic of fattyacids distilled from other crude sources, such as acidulated foots andgreases.

I have now set myself to the problem of increasing the color stabilityof fatty acids distilled from sources containing color-formingconstituents, and I have discovered ways by which the normaldiscoloration can be markedly reduced, and in many cases whollyprevented. I have been able to obtain distilled fatty acids which havecolor characteristics comparing favorably with the color characteristicsof the high grade fatty acids, and thus 1 have been able to obtain highquality fatty acids from sources hitherto regarded as commerciallyincapable of yielding fatty acids, except at great expense, which aresuitable for uses where a white material is desired.

I have discovered ways of treating the fattyacid-containing materialsprior to distillation so that the color-forming constituents therein areso modified, destroyed, or chemically converted that they either do notdistil with the fatty acids, or, if they do distil in modified form,they are rendered incapable of markedly coloring the distilled fattyacids. In other'words, the processes of my invention are diametricallyopposed to those hitherto suggested. Whereas prior workers in the arthave sought to bleach or decolorize the distilled fatty acids, I go tothe root of the problem and act upon the color-forming substances in thefatty acid source prior to such distillation. To put it another way, Ipretreat the material prior to distillation.

As stated, the processes of the present invention are primarily directedto the treatment of the cruder materials containing free fatty acids incommercially distillable quantities. These materials include acidulatedfoots, low grade grease such as garbage grease and brown grease, andhydrolyzed fatty acid mixtures, such as autoclaved or twitchellizedblack cottonseed fatty acids. All of these products are well known inthe art. In addition, the processes of the present invention are, ofcourse, limited to those fatty acid sources which contain color-formingconstituents tending to discolor the distilled fatty acids. Suchcolor-forming constituents are present in all of the crude materialsenumerated.

In order to keep the description of my invention within reasonablebounds, I shall describe it with more specific reference to thetreatment of autoclaved black cottonseed fatty acids, it beingunderstood, however, that the processes to be described are equallyeffective inthe treatment of acidulated foots, greases and any othercrude, commercial source of free fatty acids containing color-formingsubstances tending to impart color to fatty acids distilled from suchsources.

In its broadest aspects my invention comprises the heat treatment ofcrude or waste materials containing substantial quantities of free fattyacids, and containing color-forming bodies normally tending to discolorfatty acid distillates obtained from such crude materials. I have discovered that when such crude products are heated for varying periods oftime at a temperature of about 175 C. to 225 C. they will thereaftergive fatty acid distillates having markedly improved color stability incomparison with fatty acid distillates distilled directly from the crudematerials.

For example, I beat at atmospheric pressure a batch of black autoclavedcottonseed fatty acids for three hours at a temperature of about 190 C.After this heat treatment I then distil the free fatty acids from theheated black acids with steam under vacuum. The steam distillation whichI employ is that customarily used in the distillation of fatty acids,and distillation practice in this step is so well known that I shall notdescribe it in detail.

I compare the advantages of my heat treatment prior to distillation withdistillation without such heat treatment by determining the color of thefatty acids both before and after accelerated aging. In this example,fatty acids distilled directly from the black acids (withoutpretreatment) showed a distillate color of red 0.9 and yellow 8. Afteraccelerated aging at 120 C. for one hour the distillate was red 11 andyellow 30. When I pretreat the black fatty acids by heating, asdescribed above, prior to distillation, and then distil, the distillateis red 1.7 and yellow 8. After accelerated agingfor one hour at 120 C.the distillate is red 3.6 and yellow 20. This shows a marked improvementin the color stability of the fatty acids.

This broadest aspect of my invention is, of course, subject tomodifications. The length of time the fatty acid-containing materialsshould be heated will naturally vary with the material treated. If thecolor constituents appear to be present in large quantities, a somewhatlonger heating period will be necessary, up to five or six hours, forexample. at temperatures much in excess of 250 C., since this may resultin decomposition of the fatty material. It is to be expected that thosepractising my invention will make brief tests on batches of fatty acidcontaining materials in order to determine the best time and temperaturein accordance with the principles which I have laid down.

At this point I wish to distinguish from methods hitherto proposed forthe heat treatment of fats and fatty oils. It is not new to heat treatfats for the precipitation of albuminous mate- Ordinarily I do not heatrials therein, and in such heat treatment there may be some incidentaldistillation of free fatty acids. But the quantity of fatty acidspresent is minute. Although I am utilizing a heat treat- .ment, I amheating a class of substances not hitherto treated in this way. No onehas hitherto heat-treated commercial sources of free fatty acids priorto distillation for the express purpose of so changing or modifyingvolatile color constituents therein that they no longer color thedistilled fatty acids.

This phase of my invention is also not to be confused with the ordinarydistillation of free fatty acids since in that case insufiicient time isgiven for the conversion of the color constituents to harmlesssubstances. In the distillation they tend to distill out directly alongwith the fatty acids and thus contaminate the distillates.

The heat treatment described above, while beneficial, is greatlyimproved when catalysts are present in the mixture. I have discoveredthat better results are obtained when the fatty acid-containing materialis heated at the temperatures specified above in the presence of about0.5 percent of nickel-containing catalysts. These catalysts can benickel catalysts ordinarily used in the hydrogenation of oils or theycan be, and advantageously are, spent nickel catalysts which are nolonger efiective for the hydrogenation of oils. Thus, for example,autoclaved black cottonseed fatty acids when heated for three hours at180 C. in the presence of 0.5 percent of a hydrogenation catalyst of thenickel type, will give, on distillation, fatty acids which, afteraccelerated aging, show a red of 2.8 and a yellow of 10. It is apparentthat the color of these fatty acids, after accelerated aging, issomewhat better than that when no catalyst is present.

I do not, however, regard the heat treatment in the absence of acatalyst equivalent to the heat. treatment in the presence of acatalyst. In the first place it is obvious from calorimeter analysis ofthe distilled fatty acids that marked improvement is obtained by the useof a catalyst. In the second place I believe that the catalyst exerts adefinite catalytic effect on the color bodies in the initial material sothat polymerization, or conversion to substances no longer distillingwith the fatty acids, is greatly facilitated.

Garbage grease and acidulated foots can, of course, be similarly heattreated either with or without a catalyst and the fatty acids thendistilled therefrom. Neutral glycerides are constituents of such greasesand foots and I can split these glycerides to liberate furtherquantities of free fatty acids after'the distillation of the originalfatty acids in the material. Or I can subject the original material,prior to heat treatment, to a splitting, hydrolysis, or saponification,in the usual way, recover crude fatty acids therefrom, and then subjectthe crude fatty acids to the heat treatment prior to distillatlon.

It is sometimes advantageous to introduce an inert gas such as nitrogenor carbon dioxide into the fatty acid-containing material during theheat treatment described. Steam, and even air, is also beneficial inaiding in the conversion of color-forming bodies to harmless substancesand, in the appended claims, heat treating, of course, is intended tobroadly include heat treating in the presence of these added gases.

' I shall now describe still further modifications of my invention whichare superior to those just described. I have discovered that the bestresults are obtained when the fatty acid-containing material issubjected to the action of hydrogen gas in the presence of a catalyst atelevated temperatures and pressures.

For example, I treat autoclaved black cottonseed fatty acids withhydrogen for two hours at a temperature of about 200 C. and under apressure of 75 pounds per square inch inthe presence of 0.5 percent of ahydrogenation catalyst such as the nickel-bearing type. Free fatty acidsdistilled from such a pre-treate'd source of fatty acids show, onaccelerated aging at C. for one hour, a red of 1 and a yellow 01' 5.This, it may be noted, is very much better than that obtained by thesimple heat operation previously described.

This hydrogen treatment is susceptible to a number of modifications. Ineed not operate at pressures above atmospheric. I can, for instance,work at ordinary pressure, and I can vary the pressure from atmosphericto 75 pounds per square inch or higher. Similarly, I can vary thetemperature from about C. to 200 C. or 225 C. and obtain good results.The length of time is also not particularly critical although it will begoverned, of course, by the nature of the materi al undergoingtreatment. Ordinarily, about 2 to 3 hours is sufficient at elevatedpressures of the order of 50 to '75pounds. At atmospheric pressure Ifind that the time is somewhat extended and about six hours is best.Likewise,

at a temperature of C. a somewhat longer time is desirable. Thus, forexample, black fatty acids can be heated at 150 C. at atmosphericpressure for six hours in the presence 'of 0.1 percent of anickel-chromium catalyst and will give a fatty acid distillate which,after accelerated aging, shows a red of 3.9 and a yellow of 9.

The catalysts which I use are advantageously those useful inhydrogenating fats and fatty modification of my invention resides in thefact that spent catalysts from a hydrogenation operation can be usedmost effectively. That is to say, I can use catalysts which are nolonger. efiective in the hydrogenation of fats and fatty oils.

This modification of my invention should be clearly distinguished fromthe ordinary hydrogenation of Vegetable and animal oils. It is veryunusual .to hydrogenate materials containing large quantities of freefatty acids. Most' of the catalysts, such as those mentioned above, arepoisoned by the presence of free fatty acids and other impurities in themixture undergoing hydrogenation. In this modification of my invention Iam not hydrogenating any fat, fatty oil, or free fatty acid to anysubstantial extent. The iodine number of the materials which I treatwith hydrogen does not drop, or will not drop more than a few points,usually notmore than 1 or 2, and at the most 15 or 20. This means thatthe hydrogen treatment which I use is not hydrogenation at all in theordinary sense. Were there hydrogenation, the iodine number of the oleicacid present, for instance, would decrease greatly. The drop in iodinenumber may possibly be due to hydrogen absorption by the color bodies ifthey be highly unsaturated, and have iodine values of the order of threehundred. There maybe, of course, some slight incidental absorption ofhydrogen by the fatty material itself but I endeavor to keep this as lowas possible. When treating cottonseed fatty acids, the final productscontain large amounts of oleic and linoleic acid, thus indicating thatthe stabilization treatment by the present invention is not comparablewith the more or less complete satu ration of these components inordinary hydrogenation processes.

Moreover the amount of hydrogen which I use is very low. For example,for a charge of 35,000 pounds of autoclaved cotton seed fatty acids only2,800 cubic feet of hydrogen is necessary.

In one commercial adaptation of my process I charge an autoclave with25,000 pounds of twitchellized black cottonseed fatty acids containingabout 1 percent of a spent nickel catalyst from an ordinaryhydrogenation-of-oils process. This catalyst is no longer effective tohydrogenate unsaturated fats or fatty acids. I then heat the charge toabout 130 C.-l50 C. and pass in hydrogen gas so that the pressure in theautoclave is maintained at '75 pounds per square inch. The hydrogen iskept in contact with the charge for two hours and thirty minutes at 75pounds pressure, and at the temperature stated. Then the temperature isallowed to fall and the'batch kept in the atmosphere of hydrogen foranother hour and thirty minutes. Thereupon the catalyst is, if desired,filtered out of-the treated charge for reuse and the fatty acidsdistilled. The total amount of hydrogen used is 1,760 cubic feet.

The original iodine number of the charge is 105.6. The final iodinenumber, after the hydrogen treatment is 102.8, a decrease of but 2.8,which indicates practically no hydrogenation of any unsaturated fats orfatty acids. Fatty acids distilled from the original material withoutthe hydrogen treatment show a red of 2.7 and a yellow of 9 afteraccelerated aging. Fatty acids distilled from the hydrogen-treatedmaterial show a red of 0.9 and a yellow of 4 after accelerated aging.

Just what happens in this hydrogen treatment is not clear but I believethat, as stated above, the color bodies present in the crude fatty acidmaterial are possibly highly unsaturated and hydrogen may unite withthem to form compounds less highly saturated and which no longer ,havethe property of distilling over with the fatty acids and developingcolor. These color forming bodies may possible be latent color bodies.That is to say, they may be initially colorless, but on contact withair, they may go over to colored compounds. The saturated latent colorbodies may possibly distil with the free fatty acids but, because theyare now saturated, they no longer develop color on aging.

The hydrogen treatment in the presence of a catalyst is to be regardedas a distinct specie of my invention and is not equivalent to the simpleheat treatment described above. In the simple heat treatment I aminclined to believe that the color bodies or latent color bodies areeither chemically decomposed, oxidized, or polymerized to formsubstances which quite possibly no longer vaporize with the free fattyacids. In the case of the hydrogen treatment it is more likely that thecolor bodies are saturated with hydrogen to give substances which do notdevelop color in the presence of air or light and hence it does notmatter whether they distil with the free fatty acids or remain in theresidue. What actually happens is, of course, not definitely known, andI do not intend to be bound by any theories presented.

Although the above hydrogen treatment in the presence of a catalystgives me the best results, I need not always have a catalyst present.For example, when autoclaved black cottonseed fatty acids are heatedwith hydrogen at 50 pounds pressure at 180 C. for three hours in theabsence of any catalyst, the color of the fatty acid distillate afteraccelerated aging is red 4.3 and yellow 10. This is in contrast toautoclaved black cottonseed fatty acids directly distilled without anypreliminary treatment, and which show on accelerated aging underidentical conditions a red of 11 and a yellow of 30, and is furtherevidence that the action, whatever it may be, is not a hydrogenation inthe ordinary sense of the word.

When using catalysts, the catalyst can be recovered for reuse byfiltering it from the distillation residue, or it can be recovered fromthe treated material prior to distillation, and I am able to use thecatalyst over and over again as many as ten times without noticing anyparticular lessening in efiiciency. I can also use hydrogen-containinggases such as water gas.

When I employ gas treatment, such as hydrogen, nitrogen, air, or steam Iuse apparatus by means of which the batch of material under treatmentcan be agitated or stirred. This method of achieving better liquid-gascontact is, of

course, conventional and I do not describe it in detail. During the heattreatment, whether it be in the presence or absence of a catalyst, oradded gas, there is practically no distillation. I deliberately avoidthe distillation of any considerable quantity of fatty acids during thepreliminary heat treatment since otherwise the benefit of my inventionwould be naturally lessened. In other words, I- do not wish to distilthe free fatty acids until the color constituents in the mixture havebeen so modified that they will not cause coloration in the fatty acidsafter distillation thereof. In the appended table I summarize resultsobtained with the various methods described herein, and also giveadditional examples.

Treatment of autoclaved black cottonseed fatty aczd Color of distillategggg a g after aging one Treatment prior to dis M 110111 at 120 C.

tillation Red Yellow Red Yellow Control-no treatment. 0, 9 3 11, 30

l. Heated 3 hours at 190 C.

o c alyst or s 1. 7 s 3. c 20 2. Same as l but 0.5 percent Nicatalyst 1. 2 8 2. 4 l0 3. Heated at 180 0. Steam at atmos. pressure.0.5 percent Ni catalyst- 1. 9 12 5. 2 l7 4. Heated 3 hours at 180 0.

Hydrogen 50 pounds pressure. No catalyst. 1. 5 l0 4. 3 l0 5. Heated withnitrogen [or 6 hours at 150 C.atmos. pressure. 1 percent Ni catalyst 0.9 9 4. 6 15 6. Stirred with hydrogen for fihours at 150 C. atmos.pressure. 1 percent Ni catalyst 0. 7 4. 4 l3 7. Stirred with water gasfor Bhours at 150 C. etmos. pressure. 1 percent Ni catalyst 0. 8 9 3. 810 8. Heat 2 hours at 200 C. in hydrogen at 50 pounds pressure with 0.5per cent Ni catalyst 0. 7 4 l. 4 6 9. Same as 8 but 75 pounds pressure0.7 3 1.0 5 10. Heat 3 hours at 180 C. in

hydrogen at 50 pounds pressure with 0.1 percent Ni catalyst l. 0 5 1. 9S 11. Same as 10 but 0.05 percent catalyst 1. 0 7 2. 5 10 In the abovetable it is to be noted that the color of the distillate both before andafter accelerated aging is given. This will show the marked improvementobtained by the process of the present invention.

In the above table data for black cottonseed fatty acids is given indetail. Fatty acids of improved color-stability can be obtained in likemanner from the many other sources of fatty acids described above. Whendealing with mixtures containing substantial amounts of neutral fats, Ican hydrogen-treat the original material, steam distil the fatty acids,and then split the still residue (neutral fat) or I can split theoriginal material, recover crude black fatty acids therefrom and thenhydrogen-treat the fatty acids as I have described. In other words, whenmy origi nal starting material contains considerable fat, I can firsthydrolyze the fat and recover all available fatty acid (both free andcombined as glycerides) from the starting material, and then heat-treatthe recovered fatty acids.

I wish to point out that my invention is not concerned with thebleaching of ordinary fats or fatty oils which contain relatively smallquantitles of free fatty acids. Such oils are substantially composed ofneutral fats and the free fatty acid therein is to be regarded as animpurity. In the refining of such fats it is customary to remove freefatty acid prior to any bleaching or decolorizing of the neutralglycerides. And the decolorized or bleached product is not distilled.There have been proposals in the pastto heat treat the neutralglycerides for. the purpose of bleaching them. In this process some freefatty acid may be formed as a by-product during the heating action anddistil out of the mixture. However, the quantity of free fatty acidsformed in this way is insignificant and is not to be regarded as acommercial source of free fatty acid. As stated, all of the materialswhich I utilize in the present invention can be regarded as commercialsources of free fatty acids. They will all contain substantialquantities offree acid, generally at least 10 percent, this being aboutthe minimum free fatty acid, as oleic, in brown grease. 'The directdistil- .lation of crude fatty acid containing materials in which theamount of fatty acid less than 10 percent is not commercially practical.Hence the processes of the present invention are to be distinguishedfrom the. bleaching or decolorizing of the substantially neutral fats orfatty oils in which the amount of free fatty acid is most always lessthan 10 percent.

Fatty acids obtained by the processes of the present invention, inaddition to having color stability, are also improved with respect toodorand the development of rancidity.

Having thus described my invention, what I claim is:

1. In the process of distilling fatty acids from crude mixturescontaining substantial amounts mally discoloring the distilled fattyacids, the

' steps which include subjecting the crude mixture, prior todistillation, to a heat treatment at a temperature ranging from about150 C. upward but below the decomposition temperature of the fatty acidsin the presence of hydrogen gas to render said color-forming bodiessubstantially less effective to discolor the distilled fatty acids, butwithout. any substantial hydrogenation of the fatty acids in saidmixture, and then distilling fatty acids of improved color stabilityfrom said heat-treated mixture.

2. The process as in claim 1 wherein the temperature during the heattreatment is of the order of 150 C. to 225 C.

3. In the process of distilling fatty acids from crude mixturescontaining substantial amounts thereof together with color-formingbodies normally discoloring the distilled fatty acids, the steps whichinclude subjecting the crude mixture, prior to distillation, to a heattreatment at a temperature ranging from about 150 C. upward but belowthe decomposition temperature of the fatty acids in the presence ofhydrogen gas and a nickelbearing catalyst to render said color-formingbodies substantially less effective to discolor the distilled fattyacids, but without any substantial hydrogenation of the fatty acids insaid mixture, and then distilling fatty acids of improved colorstability from said heat-treated mixture.

4. In the process of distilling fatty acids from crude mixturescontaining substantial amounts thereof, together with color-formingbodies normally discoloring the distilled fatty acids, the steps whichinclude subjecting the crude mix ture-prior to distillation, to a heattreatment at a temperature ranging from about 150 C. upward but belowthe decomposition temperature of the fatty acids in the presence ofhydrogen gas and a catalyst of the hydrogenation type to render saidcolor-forming bodies substantially less effective to discolor thedistilled fatty acids, but without any substantial hydrogenation of thefatty acids in said mixture, and then distilling fatty acids of improvedcolor stability from said heat-treated mixture.

5. In the process of distilling fatty acids from crude mixturescontaining substantial amounts thereof, together with color-formingbodies normally discoloring the distilled fatty acids, the steps whichinclude subjecting the crude mixture, prior to distillation, to a heattreatment at a temperature ranging from about 150 C. upward but belowthe decomposition temperature of the fatty acids in the presence'ofhydrogen gas and a spent hydrogenation catalyst to render saidcolor-forming bodies substantially less effective to discolor thedistilled fatty acids, but without any substantial hydrogenation of thefatty acids in said mixture, and then distilling fatty acids of improvedcolor stability from said Heat-treated mixture.

6. The process as in claim 3 wherein the temperature during the heattreatment is of the order of 150 C. to 225 C.

'7. The process as in claim 4 wherein the temperature during the heattreatment is of the order of 150 C. to 225 C.

8. The process as in claim 5 wherein the temperature during the heattreatment is of the order of 150 C. to 225 C.

9. In the process of distilling fatty acids from crude mixturescontaining substantial amounts thereof together with color-formingbodies normally discoloring the distilled fatty acids, the steps whichinclude subjecting the crude mixture, prior to distillation, to a heattreatment at a temperature ranging from about 150 C. upward but belowthe decomposition temperature of the fatty a temperature ranging fromabout 150 C. up-

ward but below the decomposition temperature of the fatty acids in thepresence of hydrogen and a spent catalyst of the hydrogenation type torender color-forming bodies in said mixture substantially less eflectiveto discolor the distilled fatty acids, but without any substantialhydrogenation of the fatty acids in said mixture, and then distillingfatty acids of improved color stability from said heat-treated crudemixture.

12. The process as in claim 11 wherein the temperature of the heattreatment is about 150 C. to 225 C.

13.. The process as in claim 11 wherein the temperature is about 150 C.to 225 C. and the pressure is of the order of 50 to 75 pounds per squareinch.

MADISON L. SHEELY.

